1. Field of the Invention
The present invention relates to networks and methods for increasing the speed of and enhancing session establishment.
2. Description of the Prior Art
The Technical Specification 3GPP TS 23.228 V5.O.0 (2001–04) sets forth a mechanism for providing multimedia services in packet switched communication networks. The Technical Specification is incorporated herein by reference in its entirety.
The 3GPP R5 defines Session Initiation Protocol (SIP) protocol for session establishment and control. The SIP protocol was designed with wired networks in mind and powerful clients capable of doing end to end service negotiation. Wired networks have ample bandwidths local area networks (LANs) and clients with substantial processing capability, memory and power.
Third generation Internet Protocol (IP) networks require optional use of resources such as radio frequency bandwidth and battery life. The more than sufficient bandwidth and battery capacity of wired networks does not apply to wireless networks. IP protocols such as SIP are desirably optimized to efficiently use wireless networks and terminals.
Packet switched communication networks in accordance with the aforementioned 3GPP Technical Specification, while robust in providing services utilizing the session initiation protocol (SIP), suffer from a slowed session establishment when communications during session establishment involve low speed communications such as low capacity access networks. An example of this occurs when user equipment (UE) of a caller in a robust packet switched communication network wishes to establish a session with UE of a callee in a lower capacity access or service network containing a large capacity payload transmitted by the UE of the caller. The large capacity payload slows down the session establishment with the callee in the lower capacity access or service network as a consequence of the lower capacity slower communications therein. Currently, there is no technique for enhancing the speed of session establishment when large data payloads are involved during session establishment, especially when the UE of the callee is in a lower capacity slower access network.
WO 26729 discloses providing information about an end user/terminal capabilities to the sender so that the sender may refrain from sending a wrong type, such as too large of a data file, during transmission.
The SIP RFC discloses that a terminal may place a URL in a SIP transmission instead of payload.
WO 00/51306 discloses a network which may replace a payload with a URL.
WO 27537 discloses the storing and forwarding of payloads using the SIP INFO messages.
3GPP Rel 5 and 6, which are incorporated herein by reference in their entirety, have chosen SIP as the call control protocol. SIP will be implemented in mobile devices and core network switches. Prior to SIP being chosen as the call control protocol, 3GPP R4 and 3GPP UMTS release 99, which are incorporated herein by reference in their entirety, used an enhanced version of the 2G Call Control protocol (Typically mentioned as 3G-CC).
SIP and 3G-CC have different characteristics. 3G-CC is binary protocol with a very strict definition of the messages. Typical 3G-CC messages are optimized for the wireless environment. Hence 3G-CC messages are much smaller in size (less than 40 octets per message in a majority of the cases). On the other hand, SIP is an ASCII protocol defined by the Internet Emergency Task Force (IETF). Hence, SIP is very flexible with loosely defined messages. While SIP messages are well suited for current (IP) wireline applications, SIP requires additional functions, such as compression and filtering of messages, before effective use in the wireless environment can be realized.
Even though Universal Mobile Telecommunications System (UMTS) R99 operates on a large carrier (3.84 MHz) w.r.t. 2G-GSM (200 KHz), it is typically shared with many users resulting in smaller signaling data rates per user. This signaling bandwidth is even more restricted in the GSM/EDGE Radio Access Network (GERAN) release in view of much narrower signaling channels. Studies have shown that even with compression techniques, SIP messages are quite large in size and require a significant number of bytes to complete a voice call. For example, only 75 octets of data are required to complete a GSM call, while a SIP call with compression requires 1200 octets. See SIP compression, 3GPP TSG GERAN, Tdoc GP-011198 which is incorporated herein by reference in its entirety.
It is expected that SIP users will not willingly pay for large signaling messages that are required to establish the user plane. This is also the case in 2G wireless where signaling messages are transported via common channels free of charge. Hence, the flexibility of SIP signaling messages can be abused by users to obtain free service.
Since SIP messages are ASCII, they are much more flexible regarding header requirements. Also, the size of a SIP message cannot be determined to an accuracy of one octet. A good example is the SIP INVITE request and the response message 180 (Ringing). A SIP INVITE message uses a SIP Request line or the start line, Via, To, From, Call-ID, Cseq, Subject, Contact, Content-Type, Content-Length etc. Each of the headers thereof are followed with relevant data followed with a control character to indicate the end of line. With reasonable use, the subject header is very small. However, an abusive user can insert an unlimited amount of data (even a whole article) followed by a control character to indicate the end of line. The 180 Ringing response message is also an informational message. The start line of a 180 Ringing response begins with ‘SIP/2.0 180 Ringing’, with the word Ringing being the recommended response. A significant amount of text can be inserted after the “180” without violating the SIP specification. Hence two users may be able to communicate their own messages via SIP message structures without charge.
These kind of abuses pose several problems:
a) The precious wireless medium is consumed blocking other legitimate users.
b) Increased interference can occur causing network wide capacity reductions.
c) Difficult engineering of the wireless links is the result.
d) Increased cost for other applications can occur where operators want to recover lost revenue.